Except as provided in Sentence (2) and except for doors in enclosed unheated vestibules and cold cellars, and except for glazed portions of doors, all doors that separate heated space from unheated space shall have a thermal resistance of not less than Question 9 options: a) RSI 0.7 with a storm door provided b) RSI 6.25 with a storm door c) RSI 0.7 where a storm door is not provided d) RSI 6.25 without a storm door